Lubricants, such as industrial oils, are important components of a wide variety of mechanical systems where they provide functions such as lubricating moving parts, transporting force or energy on the mechanical system, protecting parts against wear or even a combination of these.
With use over time these lubricants may become contaminated with substances with which they come into contact, for example by the ingress of foreign substances such as water in the mechanical system, by particulate matter such as that resulting from mechanical wear and the like and oxidative degradation of the base oil and additives used in the lubricants. The net result is a decrease in the performance characteristics of the lubricant with the concomitant negative impact on the mechanical device using the lubricant.
Therefore, in many industrial environments regular lubricant analysis by common laboratory methods is a standard procedure. This necessitates removing a sample of the lubricant and transporting it, typically off-site, for analysis. This procedure normally takes at least three full days before the requisite analysis is completed and a report can be obtained. Such a time lag is highly undesirable.
The art is replete with proposed methods and devices for the on-line evaluation of lubricants, especially engine oils, many of which are based on optical techniques. Because engine oils such as diesel oils are exposed to combustion products such as blow-by gasses and soot they darken severely. For example, many engine lubricants become optically opaque at pathlengths greater than a few millimeters, especially near the end of useful life of the lubricant.
Consequently the optical techniques proposed for on-line evaluation of engine oils employ thin cells typically having a pathlength less than a few millimeters.
Industrial lubricants often are used in larger volumes than engine lubricants and they are not exposed to combustion products. Therefore, darkening from soot is not a significant problem. However, in order to allow a more accurate indication of the condition of an industrial lubricant there is a need to be able to monitor a more representative sample of the lubricant than might be monitored using thin optical cells such as proposed for engine lubricants. Also, there is a need to avoid fluid flow restriction resulting form use of these optical cells.
Thus there remains a need for improvements in determining the condition of industrial lubricants.
An object, therefore, of the present invention is to provide an on-line, real-time, method for monitoring the condition of lubricants that are not exposed to combustion products such as industrial oils.
These and other objects will become apparent from the description which follows.